Substantially solid structures occur in living mammals, such as vertebrate animals and humans, as keratinized appendages to the skin. These keratinized appendages include the nails of humans, and the horns, hoofs, and claws of animals. In the living mammal, such keratinized appendages are subjected to countless traumas from the environment to which they are exposed during everyday movements.
In humans, the hardness and strength of the nails, which includes fingernails and toenails, is particularly important not only for the beauty of their appearance, but for the well-being of the individual. Embrittlement of the nails is normally associated with aging. However, various activities expose the nails to a number of materials which also adversely affect the nail's physico-mechanical condition.
For example, occupational exposure to extensive or constant wetting of the hands with soaps, detergents, solvents, chemical hair waving and coloring lotions, and insults from deliberate cosmetic applications, such as manicuring, or any like products can lead to drying, brittleness, cracking, laminating, splitting, ridging and similar damage. Additionally, certain diseases of widely different causes and symptoms can also lead to nail embrittlement or associated disfigurement owing to weakening of nail hardness and strength.
It is sometimes desirable to enhance and improve the beauty of such keratinized appendages such as the horns, hoofs and claws of living animals for show. The appearance of fingernails and toenails of humans, in particular, are frequently enhanced with decorative nail-care cosmetics, such as nail polishes, nail polish removers, nail polish bases, alkaline cuticle removers and the like. Overuse of these products can alter the nail keratin causing it to weaken, soften, split and break.
Nail-care cosmetics and nail polishes in particular, contain organic solvents that can undesirably defat or degrease the nail, i.e., remove the natural cementing substance of the nail, and so promote drying embrittlement. Past attempts to recondition the nails have included topically regreasing them by rubbing with oils or lipids. But the nail has to be degreased again in order for a new layer of polish to adhere.
In the past, remedial approaches have included applying solutions of formaldehyde or formaldehyde donors, sodium iodide, or astringents in an attempt to chemically harden the nail keratin. However, many of these chemicals can irritate the surrounding skin tissue and lead to allergies. Moreover, iodides can discolor the nails. Alternatively, the nails have been physically strengthened by applying some temporary artificial protective coating, such as a network of nylon fibers, polymers, artificial fingernails, and the like.
Numerous nail-hardening or nail-strengthening products have been made and marketed with varying degrees of success. However, many of these products do not simultaneously harden and strengthen the nail keratin and many contain organic solvents which can degrease the nails. For example, "nail-mending" kits typically consist of a non-woven cloth for application to the nail and require a solvent-based adhesive and solvent-based topcoat for such application.
There is a long-recognized need for a solvent-free nail-care cosmetic capable of simultaneously hardening and strengthening nail keratin without degreasing the nail of its natural cementum and without irritating the surrounding skin tissues. The present invention provides such a product and a method for applying the product to the keratinous surface.